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Abstract

A process for obtaining useful products from an oil shale formation that has intermixed nahcolite and dawsonite. An aqueous solution of sodium hydroxide, containing a surfactant, is injected into the formation via wells. The sodium hydroxide reacts with the nahcolite to yield a sodium carbonate solution, which is withdrawn for further processing. Thereafter the shale is retorted in situ, with controlled pyrolysis while supplying air in controlled amounts, and petroleum products are recovered. Then water is sent into the retorted formation to produce steam, which is recovered. At some stage before or after the retorting, the dawsonite is reacted with NaOH and recovered as sodium aluminate in solution, which may be hydrolyzed or carbonated above ground to precipitate hydrated alumina. Carbon dioxide may be added to the recovered sodium carbonate aboveground to precipitate sodium bicarbonate, which may be heated to form solid sodium carbonate. The calcium carbonate in the formation may be converted to calcium oxide, which is slaked and then reacted with sodium carbonate in water solution form to yield calcium carbonate and sodium hydroxide, the latter being withdrawn while the resulting calcium carbonate remains to support the overburden.

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